Police are warning people they will be prosecuted for importing knives into the country.
It comes after six parcels bound for homes in north Derbyshire were intercepted in the last month.
They contained flick knives ordered from various countries and were intercepted by customs staff before being delivered.
An investigation has been launched and the people who ordered the knives are being traced.
Another package was found to contain cocaine.
A police source said: “We want people to know that ordering knives is an offence.
“The package will be discovered, the police will be alerted and we will trace and prosecute you.”